Metallic container closure having internal pressure release function

Abstract

A metallic container closure comprising a shell of a thin metal sheet having a circular top panel wall 7 and a skirt wall 9 , and a synthetic resin liner arranged in the shell, the skirt wall 9 having a thread-forming region and an annular groove 17 positioned at an upper end portion of the thread-forming region, wherein an internal pressure release line A extending in the circumferential direction is arranged in the skirt wall 9 at a portion over the annular groove 17 , and annular bead 30 is arranged so as to pass through between the internal pressure release line A and the annular groove 17 . The metallic container closure effectively releases the gas when the pressure in the container is elevated and effectively prevents the skirt wall from being deformed at a portion where the internal pressure release line A is formed when it is being wrap-seamed with the mouth-and-neck portion of the container.

1. A metallic container closure comprising a metallic shell having a circular top panel wall made of a thin metal sheet having a tensile strength of 200 to 230 N/mm 2  and a cylindrical skirt wall hanging down from a circumferential edge of the top panel wall, and a synthetic resin liner arranged in the shell, the skirt wall of the shell having a thread-forming region and an annular groove positioned at an upper end portion of the thread-forming region, wherein:
 an internal pressure release line extending in the circumferential direction at an angle of 40 to 95 degrees is arranged in the skirt wall at a portion over the annular groove, the internal pressure release line being constituted by a plurality of slits arranged in the circumferential direction maintaining a distance and low-strength bridging portions present among the slits and having a small width in the circumferential direction so as to be broken by an elevated pressure in the container, wherein a fixing line is formed over an angle of 25 to 180 degrees in the portion on an opposite side of the internal pressure release line in the direction of diameter on an extension thereof, the reinforcing lines are formed over an angle of 10 to 55 degrees neighboring both ends of the internal pressure release line in the circumferential direction, the internal pressure release assist line is formed between the reinforcing line and the fixing line, the internal pressure release assist line being constituted by a plurality of slits extending in the circumferential direction and high-strength bridging portions positioned among the slits and having a width in the circumferential direction larger than that of the low-strength bridging portions, the fixing line being constituted by an ultra-high-strength bridging portion having a width in the circumferential direction larger than that of the high-strength bridging portion, and the reinforcing line being constituted by reinforcing bridging portions having a width larger in the circumferential direction than that of the high-strength bridging portion but is shorter in the circumferential direction than that of the ultra-high-strength bridging portion. 
 
     
     
       2. A metallic container closure comprising a metallic shell having a circular top panel wall made of a thin metal sheet having a tensile strength of 200 to 230 N/mm 2  and a cylindrical skirt wall hanging down from a circumferential edge of the top panel wall, and a synthetic resin liner arranged in the shell, the skirt wall of the shell having a thread-forming region and an annular groove positioned at an upper end portion of the thread-forming region, wherein:
 an internal pressure release line extending in the circumferential direction at an angle of 40 to 95 degrees is arranged in the skirt wall at a portion over the annular groove, the internal pressure release line being constituted by a plurality of slits arranged in the circumferential direction maintaining a distance and low-strength bridging portions present among the slits and having a small width in the circumferential direction so as to be broken by an elevated pressure in the container, wherein a fixing line is formed over an angle of 25 to 180 degrees in the portion on the opposite side of the internal pressure release line in the direction of diameter on an extension thereof, and the internal pressure release assist line is formed between the internal pressure release line and the fixing line, the internal pressure release assist line being constituted by a plurality of slits extending in the circumferential direction and high-strength bridging portion positioned among the slits and having a width larger in the circumferential direction than that of the low-strength bridging portions, and the fixing line being constituted by the ultra-high-strength bridging portions having a width larger in the circumferential direction than that of the high-strength bridging portions. 
 
     
     
       3. A metallic container closure comprising a shell of a thin metal sheet having a circular top panel wall and a cylindrical skirt wall hanging down from a circumferential edge of the top panel wall, and a synthetic resin liner arranged in the shell, the skirt wall of the shell having a thread-forming region and an annular groove positioned at an upper end portion of the thread-forming region, wherein:
 an internal pressure release line inclusive of a slit extending in the circumferential direction is arranged in the skirt wall at a portion over the annular groove, and an annular bead is arranged so as to pass through between the internal pressure release line and the annular groove; 
 wherein the annular bead extends in the horizontal direction, and 
 wherein a knurling is formed over the annular groove of the skirt wall and the internal pressure release line is formed at the upper end of the knurling; 
 wherein an internal pressure release assist line is formed on an extension in the circumferential direction of the internal pressure release line, the internal pressure release assist line being constituted by a plurality of slits extending in the circumferential direction and a high-strength bridging portion which is positioned among the slits and has a width in the circumferential direction larger than that of a low-strength bridging portion; and 
 wherein, in addition to the internal pressure release assist line, a fixing line comprising an ultra-high-strength bridging portion having a width in the circumferential direction larger than that of the high-strength bridging portion is formed on an extension of the internal pressure release line. 
 
     
     
       4. A metallic container closure according to  claim 3 , wherein the fixing line is positioned on an opposite side of the internal pressure release line in the direction of diameter. 
     
     
       5. A metallic container closure according to  claim 3 , wherein a reinforcing line is formed between the internal pressure release line and the internal pressure release assist line, and said reinforcing line comprises reinforcing a bridging portion having a width larger in the circumferential direction than that of the high-strength bridging portion but is shorter in the circumferential direction than that of the ultra-high-strength bridging portion.